1. Field of the Invention
The present invention relates generally to semiconductor memory devices, and more particularly, but not by way of limitation, to semiconductor memory devices with command signal testing features, and to methods for testing command signals that are received in a semiconductor memory device.
2. Description of the Related Art
A typical memory system comprises a semiconductor memory device (or memory module) and a memory controller. The semiconductor memory device stores data or outputs the stored data in response to a command signal applied from the memory controller. The typical memory system performs a test for all memory cells of the semiconductor memory device during a test operation to identify an address of a normal memory cell and an address of a defective memory cell.
However, errors may occur in the communication of command signals from a memory controller to a semiconductor memory device. For example, the memory controller may apply an inappropriate command, or noise may corrupt the command signals during transmission. Such errors may cause an abnormal operation of the semiconductor memory device, resulting in poor performance of the memory system.
For the foregoing reasons, there is an urgent need for testing whether command signals of the memory system are properly communicated from the memory controller to the semiconductor memory device.